Pathways are proposed to synthesize boronic acid analogs for specific peptides, where the carboxyl or amide carbons are replaced by boron. The peptides sought are ones which should bind specifically to enzyme subsites, while forming stable tetrahedral adducts with the active site serine or cysteine residues. These "transition-state" analogs should be potent, specific inhibitors for a given enzyme. No boron analogs of this type are currently available. Inhibitors are proposed for the following enzymes: (1) elastase, thought to be involved in emphysema; (2) papain, a sulfhydryl enzyme; and (3) thermolysin, a proteolytic enzyme involved in a number of important physiological processes. In addition a specific dipeptide boronic acid is proposed as a potential antibacterial. Inhibitors for elastase and papain are of the type acyl-X-Y-B(OH)2 where X and Y are amino acid residues. The inhibitor for thermolysin is of the general type benzoyl-X-B(OH)-NH-Y, where a boron replaces an amide carbon.